Problem: Luis has taken 6 quizzes and his average score so far is 80. If he gets 100, a perfect score, on the remaining 2 quizzes, what will his new average be?
If he gets 100 on the remaining quizzes, the sum of his scores will be $6 \cdot 80 + 2 \cdot 100 = 680$ His overall average will then be $680 \div 8 = 85$.